China's gross domestic product grew at an 8.1% annualized pace in the first quarter. While that's obviously a fantastic level of growth, it's down from the 8.9% pace in the fourth quarter. And it's disappointing, considering that Thursday's market rally was partly due to whispers that China's growth may not slow after all. Oops.

The China GDP number may not be a cause for alarm yet. But it will not silence the chorus of China critics who think that nation's economy is destined for a hard landing.

The slowdown may also put more pressure on China's central bank to lower its reserve requirement ratio for banks again -- or even cut interest rates.

"It is important for global sentiment that China's growth remains strong," said John Derrick, director of research for U.S. Global Investors. "If China were to be more aggressive with easing, that would be good for stocks."

The Fed can continue to keep monetary policy loose as long as inflation remains low. But while the latest round of job market data -- a pullback in hiring in March and a pickup in weekly unemployment claims -- is disheartening, those numbers are probably not weak enough to give the Fed good reason for further bond buying.

What's more, even though inflation is low, the price of consumer goods is still rising at a higher clip than wages. So the Fed can't completely write off concerns about inflation just yet. The market seems to sense that, and that may be another reason why stocks are down Friday.

"The Fed can keep current policy in place, but there is nothing hinting at deflation. So there is no ammunition for more easing right now," Derrick said.

Investors may be looking beyond the first-quarter results and worrying about whether credit quality is deteriorating once again. The level of so-called non-performing assets at JPMorgan and Wells rose slightly from the fourth quarter. That could be an ominous sign, especially if the job market loses more momentum in the coming months.

"Earnings quality is poor and non-performing assets are up, which will scare people. Charge-offs and credit costs could go up," said Christopher Whalen, senior managing director with Tangent Capital Partners, a New York firm that focuses on banks.

And then there's Google (GOOG, Fortune 500). The company's sort-of evil stock "split" is overshadowing its latest earnings. When you look at those numbers closely, there is cause for concern.

Sure, earnings topped estimates. But sales narrowly missed forecasts. And a key gauge of how much advertisers are paying Google, the cost per click, fell from both the end of the fourth quarter and the first quarter of last year.

Shares of Google slipped nearly 3% Friday. Combine Google's lackluster numbers with the banks' and it is reasonable to wonder if first-quarter earnings won't be as strong as some people thought they might be after Alcoa (AA, Fortune 500) reported a surprise profit and much better sales Tuesday.

"Profit levels are already at record highs. So Corporate America has to start showing sustainable revenue growth to justify current stock valuations. That is key. And there are considerable headwinds for companies to digest," said Adrian Cronje, chief investment officer at Balentine in Atlanta.

Add this all up -- slowing growth in China, worries about the U.S. economy and concerns that earnings can't get that much better -- and it's clear that investors still have plenty to worry about this year. And we didn't even tackle the fact that Europe's debt crisis is rearing its ugly head again.

The recent slump may still turn out to be a correction as opposed to a major market rout. But anyone that still thinks there's nothing but blue skies ahead for stocks and the economy is kidding themselves.

"There was too much enthusiasm about the economy at the beginning of the year," said Milton Ezrati, senior economist and market strategist with Lord Abbett in Jersey City, N.J. "This is a plodding recovery and earnings should reflect that. This is a wake-up call."

Best of StockTwits and reader comment of the week: The Google stock split has made some investors angry while others don't seem to care too much about it.

bradloncar: $GOOG supposedly worrying about shareholder activism is such a red herring. It's a $200B company!

The new C class of non-voting shares is strange. As I said in today's Buzz video, it may not be "evil" but it is "devious." Google's co-founders and chairman Eric Schmidt already have voting control of the company through the B shares -- which is why there is virtually no way the plan to split the stock will be defeated.

And with a $200 billion market cap, who could really buy up enough of the A shares -- with limited voting power by the way -- to make a difference? This isn't Yahoo (YHOO, Fortune 500).

OptionsHawk: $GOOG trades like 8X earnings ex-cash - that is about all u need to know...

That is true. As I wrote in my Google earnings preview piece Wednesday, the stock is cheap and the company is still growing rapidly. But the latest results show some cracks. Anyone who's worried about competition from Facebook and Apple still has reasons to be doubtful.

Nokia launched its new Lumia smartphone in the United States on Easter. A few days later, it warned that it would report a bigger quarterly loss. Shares plunged, leading some to wonder if CEO Stephen Elop, who joined the company from Microsoft (MSFT, Fortune 500) last year, can really turn the ship around.

Douglas Blake gets the reader comment of the week award for referencing a blunt term that Elop used in a memo to Nokia (NOK) employees last year.

"$NOK forgot to jump off the burning platform!," he tweeted.

Ouch. I keep waiting for Research in Motion (RIMM) to come up with a disaster metaphor of its own as well to describe the BlackBerry. Iceberg straight ahead!

The opinions expressed in this commentary are solely those of Paul R. La Monica. Other than Time Warner, the parent of CNNMoney, and Abbott Laboratories, La Monica does not own positions in any individual stocks.